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Diseases and Conditions
Special to CNN.com
You don't have to play footsie with a frog to end up with warts on your feet. Toads can't be blamed for these embarrassing bumps, either.
Plantar warts are noncancerous skin growths on the soles of your feet caused by the human papillomavirus (HPV), which enters your body through tiny cuts and breaks in your skin. Plantar warts often develop beneath pressure points in your feet, such as the heels or balls of your feet.
Most plantar warts aren't a serious health concern, but they may be bothersome or painful, and they can be resistant to treatment. You may need to see your doctor to remove them.
Signs and symptoms
Plantar warts are often mistaken for corns or calluses. To make the distinction, look for:
- Small, fleshy, grainy bumps on the soles of your feet
- Hard, flat growths with a rough surface and well-defined boundaries
- Gray or brown lumps with one or more black pinpoints, which are actually small, clotted blood vessels, not "wart seeds"
- Bumps that interrupt the normal lines and ridges in the skin of your feet
You acquire warts through direct contact with the human papillomavirus (HPV). There are more than 100 types of HPV. Some types of HPV tend to cause warts on your hands, fingers or near your fingernails. Others tend to cause warts on your feet.
The virus that causes plantar warts isn't highly contagious, but it thrives in warm, moist environments, such as shower floors, locker rooms and public swimming areas. So you may contract the virus by walking barefoot in public places.
Like other infectious diseases, HPV may also pass from person to person. If you have a plantar wart, you can even spread the virus to other places on your own foot by touching or scratching. The virus can also spread by contact with skin shed from a wart or blood from a wart.
Each person's immune system responds to warts differently, so not everyone who comes in contact with HPV develops warts. Even people in the same family react to the virus differently. That's why parents and kids don't necessarily spread warts by sharing the same shower.
These ugly bumps are more likely to appear on the feet of people with:
- Multiple exposures to the virus
- Damaged or cut skin
- Weakened immune systems
For reasons doctors don't understand, some people are more susceptible to the wart-causing virus, just as some people are more likely to catch a cold. Children and teenagers tend to be especially vulnerable to warts.
When to seek medical advice
See your doctor if your warts are painful or change in appearance or color. Also see your doctor if warts persist, multiply or recur, despite home treatment, or if warts interfere with your activities. If you have diabetes or a circulatory disorder, don't try to treat any plantar warts at home. See your doctor for advice.
In some cases, you may need to consult your doctor to ensure a correct diagnosis. It's possible for more serious lesions to crop up on your feet, including cancerous tumors called carcinomas and melanomas. If you can't confidently identify your lump, have your doctor take a look.
Screening and diagnosis
In most cases, your doctor can diagnose plantar warts just by inspecting your feet. If there's any doubt, your doctor may need to pare down the lump with a scalpel. Why? Corns and calluses don't have a blood supply and won't bleed, while plantar warts will show signs of pinpoint bleeding from their dark dots, which are really blood vessels.
If there's still doubt about the diagnosis, your doctor may take a sample of your foot tissue and send it to a laboratory for analysis.
Plantar warts can be persistent. They can shed the virus into the skin of your foot before they're treated, prompting new warts to grow as fast as the old ones disappear. The best defense is to treat new warts as quickly as possible so that they have little time to spread.
If untreated, warts can swell to an inch or more in circumference and they can spread, developing into clusters of warts called mosaic warts. They may also become extremely painful. If you have lots of plantar warts, the pain may make it difficult for you to walk or run.
Plantar warts usually go away on their own, but most people would rather treat them than wait for them to disappear. Unless you have an impaired immune system or diabetes or are pregnant, there's no reason you can't treat warts with over-the-counter remedies. But you may wish to consult your doctor for help. He or she may suggest a combination of over-the-counter and office treatments.
No wart treatment works 100 percent of the time. In general, your doctor will recommend the least painful — and least destructive — methods first, especially for children.
Common treatments for simple plantar warts
Your doctor may suggest trying these common treatments one at a time or in combination:
- Salicylic acid. Wart medications and patches are available at drugstores. To treat plantar warts, you'll need a 40 percent salicylic acid solution or patch (Curad Mediplast, Dr. Scholl's Clear Away Plantar, others), which peels off the infected skin a little bit at a time. Apply the solution once or twice each day, being careful to avoid healthy skin, which can become irritated from the acid. In between applications, pare away the dead skin and wart tissue using a pumice stone or emery board. You may need to repeat this process for up to three or four weeks to completely eliminate warts.
- Duct tape. In a well-publicized 2002 study, duct tape wiped out more warts than freezing (cryotherapy) did. Study participants who used "duct tape therapy" covered their warts in duct tape for six days, then soaked their warts in water, and gently rubbed warts with an emery board or pumice stone. They repeated this process for up to two months or until their warts went away. Researchers hypothesize that this unconventional therapy may work by irritating warts and the surrounding skin, prompting the body's immune system to attack. Today, duct tape is commonly used to treat warts, especially for children who may find freezing painful or scary. It's often combined with salicylic acid.
- Freezing (cryotherapy). Freezing is one of the most common treatments for plantar warts and is usually effective, but may require multiple trips to your doctor every two to four weeks. Your doctor can apply liquid nitrogen with a spray canister or cotton-tipped applicator. The chemical causes a blister to form around your wart, and the dead tissue sloughs off within a week or so. Freezing isn't commonly used in young children because it can be painful.
- Cantharidin. Doctors and healers have used cantharidin — a substance extracted from the blister beetle — to treat warts for centuries. Today, this therapy is sometimes paired with salicylic acid. Your doctor paints this beetle juice onto your wart and covers it with clear tape. The application is painless, but it causes the skin under the wart to blister, lifting the wart off the skin. Your doctor can then clip away the dead part of the wart in about a week. However, some doctors are hesitant to use cantharidin because it's not approved by the Food and Drug Administration for the treatment of warts.
Aggressive treatments for persistent plantar warts
If your warts don't respond to common treatments, your doctor may suggest one or more of these other options:
- Minor surgery. This involves cutting away the wart or destroying the wart by using an electric needle in a process called electrodesiccation and curettage. This treatment is effective, but may leave a scar if not done carefully. Your doctor will anesthetize your skin before this procedure.
- Laser surgery. Doctors can use several types of lasers to eliminate stubborn warts. But laser surgery is expensive and painful and may take longer to heal than other treatments.
- Immunotherapy. This therapy attempts to harness your body's natural rejection system to remove tough-to-treat warts. This can be accomplished in a couple of ways. Your doctor may inject your warts with interferon, a medication that boosts your immune system's instinct to reject warts. Or your doctor may inject your warts with a foreign substance (antigen) that stimulates your immune system. Doctors often use mump antigens, because many people are immunized against mumps. As a result, the antigen sets off an immune reaction that may fight off warts.
- Imiquimod (Aldara). This prescription cream is an immunotherapy medication that encourages your body to release immune system proteins (cytokines) to help ward off warts. You can apply this cream directly to your warts. Imiquimod is approved by the Food and Drug Administration for the treatment of genital and perianal warts, but it is also successful in treating common warts and plantar warts.
- Other medications. In severe cases that haven't cleared with other therapies, your doctor may inject each wart with a medication called bleomycin, which kills the virus. This medication is given systemically in higher doses to treat some kinds of cancer. The injections for wart treatment can be painful and can cause rashes or itching. They're not used if you're pregnant or breast-feeding or if you have circulation problems.
To reduce your risk of plantar warts:
- Avoid direct contact with warts. This includes your own warts.
- Keep your feet clean and dry. Change your shoes and socks daily.
- Don't go barefoot in public areas. Wear shoes or sandals in public pools and locker rooms.
- Don't pick at warts. Picking may spread the virus.